I just haven’t gotten to making a user interface for showing you which relics are not previewed yet.
A few people ended up with duplicate relics in their addon data… not quite sure how, but resetting your addon settings will resolve that particular issue. Instructions in this post: You have one or more relics in your bags or bank that have not been previewed at the Netherlight Crucible - #4 by yellowfive
If that doesn’t do the trick, then the second most common cause is that you really do have relics not previewed – usually on a spec you don’t use often, for a relic color only available on that spec.
If it still shows the unpreviewed relic indicator, post your addon export and we can take a closer look.